Abstract
Orchard pesticide off-target deposition and drift cause substantial soil and water pollution, and other environmental pollution. Orchard target-oriented spraying technologies have been used to reduce the deposition and drift caused by off-target spraying and control environmental pollution to within an acceptable range. Two target-oriented spraying systems based on photoelectric sensors or ultrasonic sensors were developed. Three spraying treatments of young cherry trees and adult apple trees were conducted using a commercial sprayer with a photoelectric-based target-oriented spraying system, an ultrasonic-based target-oriented spraying system or no target-oriented spraying system. A rhodamine tracer was used instead of pesticide. Filter papers were fixed in the trees and on the ground. The tracer on the filter papers was washed off to calculate the deposition distribution in the trees and on the ground. The deposition data were used to evaluate the systems and pesticide off-target deposition achieved with orchard target-oriented sprayers. The results showed that the two target-oriented spraying systems greatly reduced the ground deposition compared to that caused by off-target spraying. Compared with that from off-target spraying, the ground deposition from photoelectric-based (trunk-based) and ultrasonic-based (canopy-based) target-oriented spraying decreased by 50.63% and 38.74%, respectively, for the young fruit trees and by 21.66% and 29.87%, respectively, for the adult fruit trees. The trunk-based target-oriented detection method can be considered more suitable for young trees, whereas the canopy-based target-oriented detection method can be considered more suitable for adult trees. The maximum ground deposition occurred 1.5 m from the tree trunk at the back of the tree canopy and was caused by the high airflow at the air outlet of the sprayer. A suitable air speed and air volume at the air outlet of the sprayer can reduce pesticide deposition on the ground.
Highlights
Pests in orchards are mainly controlled through the use of chemical pesticides, which decrease fruit loss by 66% to 90% [1,2,3,4]
Because target-oriented spraying with a photoelectric sensor can only selectively spray based on the presence or absence of a tree and cannot perform variable-rate spraying based on information such as canopy profile and denseness, a target-oriented spraying system equipped with an ultrasonic sensor has been developed [11,19,20,21]
Maghsoudi et al [22] acquired the volume of fruit tree canopies in real time through ultrasonic sensors and achieved variable-rate spraying according to the change in canopy volume, cutting pesticide use by 34.5% on average to achieve spraying effectiveness similar to that of conventional spraying methods
Summary
Pests in orchards are mainly controlled through the use of chemical pesticides, which decrease fruit loss by 66% to 90% [1,2,3,4]. This requires a large amount of pesticide, and causes environmental pollution due to the drift of excess spray into the air and onto the ground [5,6,7,8] To address this problem, orchard air-assisted target-oriented spraying systems with various sensors have been developed, enabling variable-rate spraying based on information such as tree location, canopy profile and leaf density, and significantly reducing the amount of pesticides used [9,10,11]. Photoelectric sensors are the easiest to use in terms of applying target-oriented pesticide spraying in orchards They allow control of the nozzle opening by detecting the position of the tree trunk or tree canopy to achieve target-oriented spraying [12,13,14,15]. Zhu et al [27] developed a laser-guided variable-rate sprayer for managing insects in ornamental nurseries, and field tests in the three studied nurseries with three different insect pests showed that the sprayer reduced spray volume rates by 25% to 80%
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